The Mekhilta dissects a single verse about Moses' judicial role to reveal two entirely different kinds of judgment. The verse states (Exodus 18:16): "When they have a matter to be resolved, he comes to me, and I judge between a man and his neighbor."
"When they have a matter" — this, the rabbis explain, refers to questions of ritual law: cases involving uncleanliness or cleanliness, what is permitted and what is forbidden. These are matters of religious obligation where there is a definitive right answer found in the Torah. The judge does not negotiate. He determines the law and declares it.
"And I judge between a man" — this describes a judgment where there is no compromise. The case has a winner and a loser. One party is right, the other is wrong, and the judge must say so plainly. This is strict justice, din, rendered without softening the verdict.
"And his neighbor" — but then the verse uses a striking word. It does not say "between a man and his enemy" or "between a man and his opponent." It says "his neighbor." The Mekhilta explains that this refers to a different kind of judgment entirely: one involving compromise, where both parties make concessions. And the proof is in the word itself — after this kind of judgment, the two parties take leave of each other as "neighbors," their relationship preserved rather than destroyed.
Moses practiced both forms of justice. He knew when to rule strictly and when to seek peace between the parties.